Closed loop work station bioremediation using mini-reactor cartridges

ABSTRACT

A system for capturing and neutralizing HAP&#39;s (hazardous air pollutants) and VOC&#39;s (volatile organic compounds) at the source point by providing a closed loop remediation system which utilizes an air collection, treatment and control module containing a predetermined size bay of multiple interchangeable mini-biofilter cartridges that function to consume the pollutant and recirculate remediated air back to the source point of the pollutant. The system includes establishing a closed loop air system at a work station which generates and emits VOC&#39;s, capturing the VOC&#39;s in the air stream flow and transporting them directly into an adjacent biofilter module which contains selected microorganisms in mini-cartridges which biodegrade said VOC&#39;s and recirculates remediated air back to the source point of the pollutant.

BACKGROUND OF THE INVENTION

[0001] The present invention relates in general to a system for removaland treatment of pollutants in air, and more specifically to a sourcepoint closed loop remediation system. With respect to HAP (hazardous airpollutants) and VOC (volatile organic compounds) current methods of VOCremoval include distillation; oxidation combustion ionization;biofiltration; and activated carbon adsorption. All of these methods arelarge whole-building fixed systems having high installation costs, and,with the exception of biofiltration, have high energy consumption andintroduce new pollution considerations or generate hazardous waste.

[0002] The present invention includes the use of multiple smallmini-reactor cartridges to reduce installation and repair or replacementand maintenance costs, permit incremental system expansion, and allow avariety of suitable mini-reactor based remediation technologies to beused together in series or parallel.

[0003] Present systems typically treat and exhaust an entire volume ofbuilding air without considering the actual pollution source andconcentration, resulting in inefficient pollution removal. Furthermore,air heating or cooling of the makeup building air is required which addsto total energy consumed.

[0004] Biofiltration utilizes the natural process of biodegradationwhich in its most basic form occurs in a compost pile. Most typically,water-borne microbes consume the carbon in the organic matter of thepile, and release carbon dioxide and water. By passing an airstreamcontaining an organic vapor (HAP/VOC) containing carbons through such acompost pile, the microbes will preferentially consume the more readilyavailable carbon in the gas stream, thereby cleansing said airstream.

[0005] Notwithstanding initial installation costs, biofiltration is aproven and low energy cost, natural method of HAP/VOC remediation thathas been in commercial use in large installations both in the UnitedStates and abroad for over 15 years. In biofiltration, no secondarycarbon source (natural gas) is required to maintain combustion and makeup for varying concentrations of VOC laden air as in the most widelyemployed oxidation process; and no hazardous waste is generated as withcarbon absorption; and no by-products other than water and carbondioxide are released. Distillation is usually not economically practicaldue to relatively low work place concentrations and value of therecovered chemical.

[0006] Because of their large size and method of construction andoperation, current bioremediation systems have relatively highinstallation, secondary energy consumption and operational costsapproaching the other methods.

[0007] Current biofiltration technology includes the use of naturallybiodegradable media such as compost and vegetation as the supportingmedia and the source of both microbes and nutrients, and has proven tohave inconsistent and relatively uncontrollable and repeatable long termfield performance.

[0008] The present invention includes complete control of the microbialenvironment with the use of stable artificial media in conjunction withcontrolled water and nutrient addition for consistent operation. Thepresent invention further includes the inoculation of said environmentwith specifically isolated and custom grown inoculate tailored to theVOC/HAP to be remediated to maintain high and consistent removalefficiency.

[0009] With respect to bioremediation, the following prior art isrepresentative of the state of the art with respect to treating HAP'sand VOC's.

[0010] U.S. Pat. No. 3,880,061 broadly relates to a contamination freework station by providing an air stream across the work station toremove any contaminants through filter means as shown in the figure.

[0011] U.S. Pat. No. 4,734,111 is directed to a process and apparatusfor cleaning spent air or air polluted with styrene and filtering outthe styrene in an apparatus and process which uses a specific biofilterutilizing a spruce bark and microorganisms thereon to degrade thestyrene.

[0012] U.S. Pat. No. 5,409,834 relates to an invention and apparatus forremoving pollutants from a source of polluted air such as a work paintstation (see FIG. 1). Polluted air from the work station is introducedfrom a supply conduit into a wet plenum chamber which has a spray nozzlewhich sprays microbial laden liquid into the incoming polluted air.

[0013] U.S. Pat. No. 5,691,192 is related to a biological filter forremoving volatile compounds from gas emissions such as styrene. Thestyrene is broken down with a fungus which is contained on a carrier orinert material such as perlite. Activated carbon may also be added tothe mixture.

[0014] U.S. Pat. No. 5,869,323 is directed to a biofilter which uses abioreactor treatment tank comprising at least one bioreactor bed and inwhich the air filtration is conducted such that the air flow through thetank is from the top downward, with the biofiltration being conductedunder pressures of less than an ambient.

[0015] These inventions teach the conventional type of prior art systemswhich are used for aerobic bioremediation in commercial plants. All theabove, and this patent pertain to aerobic biofiltration wherein thebiodegradation occurs on the surface of a water film by a consortium ofaerobic microbes.

[0016] U.S. Pat. No. 6,010,900 is directed to enhancing biodegradationusing a bioreactor. The bioreactor contains an aqueous phase in which amicroorganism capable of degrading a sparingly soluble volatile organiccompound is contained. The patent further teaches contacting thesolution with a gas/vapor stream comprising the sparingly solublevolatile organic compound such that the soluble volatile organic issolubilized in the aqueous phase to form an enriched solution, and thenincubating the enriched solution so that the microorganism degrades thesolubilized sparingly soluble volatile organic compound therebyenhancing biodegradation. (This is an anaerobic process and is notrelated to the present invention).

[0017] It can therefore be seen from the above cited commercialpractices and prior art that there is a need for a bioremediation systemwhich reduces natural gas and energy consumption and high fixed andoperation costs of remediation; adds efficiency, control andrepeatability to the bioremenation process; and does not producehazardous waste by-products as is typical of the current prior artsystems.

SUMMARY OF THE INVENTION

[0018] It is therefore an object of the present invention to provide ashipable by common carrier, expandable, movable, modular components,cartridge based closed loop system for remediation of HAP/VOC's within amanufacturing plant at the source.

[0019] It is another object of the present invention to provide anefficient biological system which reduces HAP/VOC's to water and carbondioxide.

[0020] It is another object of the present invention to remediateprocess HAP/VOC's concentration over 90%.

[0021] It is yet another object of the present invention to provide asystem for collection and neutralizing HAP's (hazardous air pollutants)and VOC's (volatile organic compounds) at the source point.

[0022] Another object is to contain the biological eco-system inmultiple small biofilter cartridges.

[0023] Another object is to use an artificial support media for thewater film that supplies no naturally biodegradable matter and thereforewill not degrade or compact.

[0024] Another object is the use of specifically isolated inoculatecontaining highly efficient microbe strain(s) tailored to maximallyconsume the VOC/HAP to be remediated.

[0025] Another object is to provide appropriate nutrient addition toenhance microbial growth.

[0026] Another object is to provide and maintain a suitable water filmto the media to sustain the inoculate eco-system.

[0027] Another object is to replenish the media water film byperiodically and discontinuously bio-recirculating inoculate andnutrient laden water through the media at a low flow rate.

[0028] Another object is to flush excess biomass and cleanse andreactivate the media by periodically and discontinuously filtering andrecirculating inoculate and nutrient laden water through the media at ahigh flow rate.

[0029] Another object is to collect, filter, store, replenish andrecirculate the nutrient and inoculate laden water within a remediationsystem at the work station.

[0030] Another object is to allow reversal of the airstream flow throughthe reactor cartridges.

[0031] Another object is to contain air and water functions inremediation modules.

[0032] Another object is to allow top-to-bottom physical reversal of thereactor cartridge in the system.

[0033] Another object is to allow system reversal of the airstreamdirection through the cartridge.

[0034] Another object is to allow for series and/or parallel airflowthrough multiple cartridges.

[0035] Another object is to allow various cartridges to containdiffering media, inoculate, and/or remediation methods.

[0036] Another object is to allow individual replacement of a singlecartridge in a remediation system.

[0037] Another object is to use the mini-reactor cartridge embodimentfor other granular remediation techniques.

[0038] Another object is to include exhaust stream dehumidifcation.

[0039] Another object is to combine all remediation system functions ina single cartridge assembly.

[0040] The present invention is directed to providing a closed loopmodular remediation system which includes air collection with air andwater treatment and control and contains a predetermined size bay ofmultiple interchangeable minibiofilter cartridges that function toconsume the pollutant and recirculate remediated air back to the sourcepoint of the pollutant.

[0041] In one embodiment, a closed loop air stream is established at awork station area involving fiberglass laminating which generates andemits the styrene HAP, which is captured by the air stream flow whichtransports the emitted styrene directly into an adjacent biofiltermodule system as described above which contains selected microorganismsin multiple mini-biofilter cartridges which consume the styrene, andrecirculates the remediated air back to the source point of thepollutant at the work station. The air flow is continuous and the systemserves to maintain the styrene level at the work station at safe levels.

[0042] In a further embodiment, multiple sources of contaminants in agiven room or area can be captured and treated at a single remediationstation or multiple remediation stations can be used within a given roomor area to treat higher concentrations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] For a further understanding of these and objects of theinvention, reference will be made to the following detailed descriptionof the invention which is to be read in connection with the accompanyingdrawing, wherein:

[0044]FIG. 1 is a front view with partial break away of a self-containedair collection, treatment and control module containing multiplebiofilter cartridges used in the system of the present invention.

[0045]FIG. 2 is a schematic side view of a self-contained singlecartridge remediating system for treating a small source.

DETAILED DESCRIPTION OF THE INVENTION

[0046] The present invention is more fully understood with reference tothe drawings where FIG. 1 illustrates a closed loop system 10 fortreating a work station area or room 12 which contains a source ofpollutant such as styrene generated from laminating with fiberglass. Theclosed loop ducting system contains an array of interchangeablemini-biofilter cartridges 14 which contain a carrier medium 16supporting a water film suitable for microorganisms or a mix ofmicroorganisms on the carrier surface which have been selected todegrade the styrene or other VOC's of interest. The cartridge(s) ispreferentially filled with a suitable inert carrier material such asperlite or an inert synthetic material such as plastic or a ceramic. Amoisturized and nutrientzed airflow through the biofilter promotes thegrowth of indigenous or synthesized microorganisms on the surface of thecarrier material which through the action of the microorganisms acts tobiodegrade the HAP and/or VOC's of interest. Suitable microorganismswhich can be used to promote this degradation include bacteria, such asPseudomonas and Mycobacterium. Other suitable natural occurringmaterials which contain indigenous microorganisms such as compost, peat,soil, wood chips, plant residues and tree bark may also be used orincluded. The reversible biofilters contain an outer housing or shell 15suitability made of plastic and contain a perforated top and bottom, 18and 20 respectively, which may include a screen to allow for air flowand water flow through the biofilter. Interconnecting ducting 22 passesa flow of contaminated air from the room through the bottom of thebiofilters with remediated air passing back into the room throughducting 24. Pump 25 functions to recirculate and replenish theinoculated nutrient laden water film on the carrier material in thebiofilters which enhances the action of the microorganisms in degradingthe styrene. Pump 25 preferentially draws water from lower collectiontrough 28 which has received excess water from the biolfilters 14. Pump25 then recirculates the water to the top of the biofilter through watermanifold 30 and nozzles 32. In FIG. 1, which is not drawn to scale, areaor room 12 is depicted as grossly smaller in size than the closed loopsystem 10. For example the cartridges 14 are typically about 30 inchesin height and 15 inches×15 inches in cross-section. The discrepancy inrelative sizes is to better show the detail of the closed loop system.

[0047] In a further embodiment of the present invention as shown in FIG.2, a single independent mini-reactor cartridge 40 is illustrated. Thecartridge contains an outer housing 42 and is open at both ends 44 and46 with supporting grilles (not shown) to contain the carrier media. Thecartridge contains an upper clip-on blower housing 48 which contains anexhaust fan 50 and an exhaust port 52. The blower housing is attached tothe cartridge by latch 54 and ring seal 56. A water reservoir 58 isattached to the bottom of cartridge 40 by latch 60 and ring seal 62. Thereservoir contains water 64 and optionally a wicking humidifier filter66. In operation, air to be treated is drawn in through inlet 68 andhumidified in reservoir 58. A suitable source of microorganismscontained on a carrier media 70 in the housing degrade the VOC ofinterest as previously described herein. The arrows in the drawingdepict the flow path with the remediated air passing through media 70and exiting through exhaust port 52.

[0048] A water recirculation pump 72 and associated water transfermanifold 74 may optionally be added to recirculate the microbe andnutrient laden water from the reservoir 58 to the top of the reactorcartridge 40. Optionally dehumidification may be required to lower exitair moisture buildup.

[0049] A single cartridge system of the type shown in FIG. 2 was usedfor evaluation and testing. The mini-reactor cartridge measured 15″square and 30″ tall with 8-½″ square inlet and outlet grilled openingsat opposite ends. The nominal inside volume of the cartridge wasapproximately 3.6 cubic feet. The cartridge with a bottom grilleinstalled, weighs approximately 16 pounds. The reactor was then loadedwith 30 pounds of coarse perlite media, for a total cartridge plus mediadry weight of about 46 pounds.

[0050] The blower housing as shown in FIG. 2 was attached to the top ofthe cartridge along with a water replenishment port and waterrecirculating hose, and a small water recirculating submergible pump wasinstalled in the water reservoir. The system was assembled by placingthe cartridge on top of the water reservoir and then adding the blowerhousing on top of the cartridge to make up a basic system as describedin FIG. 2.

[0051] The system parameters were then adjusted to achieve a 5 CFMairflow giving a nominal 45 second empty bed dwell time. The water flowwas set at a nominal flow of 8 oz./hr. to supply sufficient bed moisturein the range of 4 oz./hr. to account for evaporation due to a 40% RHambient air, plus an additional 100% excess to maintain some tricklingflow through the bed.

[0052] The system was then loaded with 2 gallons of inoculate andnutrient mixed in water. The inoculate used was Pseudomonas Putida whichis capable of growth on toluene and is grown on a dilute minimal mediumusing styrene as a sole carbon and energy source. The inoculate is usedin a concentration of about 108 CFU/ml and introduced to the cartridgeby trickling over the perlite. The nutrient used was a common slowrelease granular garden fertilizer sold by Agway under the trade nameOsomocote.

[0053] A standard styrene source which releases 100 PPM styrene at 5 CFMwas connected to the inlet port, and the system blower and pump werestarted up. Measurements were taken with a photo-ionization detector(PID) at the inlet and outlet of the system. Within 1 hour of startup,the average concentration in the outlet stream was 18 PPM, and after 24hours had dropped under 9 PPM for a 90%+ reduction in styreneconcentration.

[0054] Earlier lab tests made on a similar size configuration set to thesame airflow dwell time parameters, but using a horizontal lab reactorloaded with oak chips and natural compost, and with no water tricklingor inoculate addition achieved a 75% removal rate after 7 days ofoperation, and maintained in that range for over 2 months until the testwas terminated due to the bed drying out.

[0055] Another lab test using the same lab reactor and test setup andloaded with oak chips, and the inoculate, had faster startup results onthe order of 4 days and better long term remediation on the order of85%, until the natural bed settled and bed channeling occurred some timeafter 3 months. This was indicated by a decrease in remediation down to80%. Disassembly of the reactor confirmed the channeling along with somebed dryup and compaction.

[0056] A further lab test using the same lab and test setup was loadedwith plastic pellets and a water pump added to recirculate the waterfrom the bottom of the reactor to the top. The Pseudomonas Putidainoculate described above was used with the addition of a slow releasenutrient. Initial startup time was on the order of 2 days to reach a 80%removal rate, with 90% being reached after 4 days. The reactorefficiency continued to increase. Pump failure eventually occurred afteranother 10 days at which point the removal rate was up to 94%.

[0057] It should be understood that the present invention is not to belimited by the preferred embodiments of the mini-cartridge, which may beincreased in size up to a maximum weight and volume that can be put on apallet, moved by a factory pallet jack or fork lift, and shipped bycommon carrier. This is as opposed to current large permanent singlereactor designs requiring a pit or rigging to install.

[0058] While the present invention has been particularly shown anddescribed with reference to the preferred mode as illustrated in thedrawing, it will be understood by one skilled in the art that variouschanges in detail and configuration may be effected therein withoutdeparting from the spirit and scope of the invention as defined by theclaims.

We claim:
 1. A self-contained system for capturing and neutralizingHAP's (hazardous air pollutants) and VOC's (volatile organic compounds)at the source point by providing a closed loop remediation system whichutilizes an air collection treatment and control module containing apredetermined size bay of multiple interchangeable mini-biofiltercartridges that function to sustain microbial activity that will consumethe pollutant and recirculate remediated air back to the source point ofthe pollutant, said method comprising; establishing a closed loop airsystem at a work area which generates and emits HAP/VOC's, capturingsaid HAP/VOC's in said air stream flow and transporting said HAP/VOC'sdirectly into an adjacent biofilter system which contains cartridgescontaining selected microorganisms which biodegrade said HAP/VOC's andrecirculates remediated air back to the source point of the pollutant atsaid work station, with said air flow being continuous and whichfunctions to maintain the VOC level at said work station at a safelevel.
 2. The system of claim 1 in which the cartridges are positionedvertically and water is discontinuously recirculated through themicroorganisms at a slow rate.
 3. The system of claim 1 where water isperiodically flushed through the microorganisms at a fast rate.
 4. Thesystem of claim 1 where said water is filtered and recirculated.
 5. Thesystem of claim 1 which uses same source of water for recirculation andflushing.
 6. The system of claim 1 where the gas to be remediated isselected from the group of HAP/VOC's including carbon in their molecularstructure such as styrene.
 7. The system of claim 1 in which themicroorganisms are at least one isolated from the group consisting ofbacteria.
 8. The system of claim 1 in which the cartridges are sized soas to be easily shipped by common carrier and installed by hand or withpallet jack or fork lift.
 9. The system of claim 1 in which theremediated air is dehumidified.
 10. The system of claim 1 in which theair flow is periodically reversed.
 11. The system of claim 1 in whichthe cartridges are positioned vertically and water is trickled throughthe microorganisms.
 12. The system of claim 2 in which the microorganismladen water film is supported on a carrier material.
 13. The system ofclaim 12 in which the carrier is at least one artificial materialselected from the group consisting of granular inert plastics.
 14. Thesystem of claim 12 in which the carrier is at least one artificialmaterial selected from the group consisting of granular elastomers orrubbers (i.e., tires).
 15. The system of claim 12 in which the carrieris at least one artificial material selected from the group consistingof granular minerals.
 16. The system of claim 12 in which the carrier isat least one artificial material selected from the group consisting ofcrystalline minerals.
 17. The system of claim 12 in which the carriermay include at least one natural material selected from a groupconsisting of biodegradable media such as compost, tree bark andvegetation.
 18. A work station which generates HAP's and/or VOC's andremediates the pollutants and toxins on site which comprises; (a)providing a work station which generates HAP's and/or VOC's (b)establishing a closed loop air system which captures said HAP/VOC's (c)at least one biofilter cartridge positioned adjacent to said workstation and connected to said closed loop air system, wherein saidcartridge contains a source of selected microorganisms which degradesaid HAP/VOC's; and (d) where in operation, captured HAP/VOC's aretransported to and through said system and cartridges and whichrecirculates remediated air back to the source point of the pollutant atsaid work station.
 19. A mini-reactor cartridge which comprises an outerhousing having a pair of oppositely disposed open ends, a blower housingwhich contains an exhaust fan and an exhaust port positioned at one end,and a water reservoir attached to said opposite end with said reservoirfurther containing an inlet for a source of air to be treated, where inoperation, air to be treated is passed through said inlet and passedthrough a suitable source of microorganisms contained in said housingwhich degrade the VOC of interest, with said treated air being releasedthrough said exhaust port.
 20. The cartridge of claim 19 in which thefan is positioned at the inlet end of the cartridge.
 21. The cartridgeof claim 19 where inlet air is humidified by said reservoir.
 22. Anelongated portable cartridge having a sealed outer housing and twoopposite ends which are open to allow for the passage of an air flow,said housing containing a source of microorganisms contained on acarrier media, with said microorganisms being adapted to biodegradeselected HAP's and VOC's of interest, with said cartridge being of asize and weight to enable a person of average size and weight to handleand maneuver said cartridge, with the ends of said cartridge beingadapted for connection to a closed loop air system which captures andtransports VOC's in said air stream to and from said cartridge fortreatment.